1. Technical Field
The present invention relates to a technique using optical scanning. For example, the invention relates to an optical scanning apparatus and an image forming apparatus.
2. Related Art
An optical scanner is known as an example of an optical device which performs drawing by using optical scan in a laser printer and the like. The optical scanner can be formed by processing a silicon substrate by micro electro mechanical systems (MEMS), for example. Such the optical scanner can project and display an image or a video picture on a flat surface (a screen) by performing optical scan in a double-axis (X axis and Y axis, for example) direction (hereinafter, referred to as X-Y scan).
However, in a case where a surface (screen) on which an image or a video picture is projected is a spherical surface, a curved surface, or the like in a three-dimensional shape such as a sphere, a hemisphere, and a cylinder, the X-Y scan may be inefficient. When the X-Y scan is performed with respect to a hemispherical screen shown in FIG. 8, for example, light is scanned not only on a region inside the screen but also on a region outside the screen as shown by diagonal lines in FIG. 9. In this case, light scanned on the outside of the screen as shown by the diagonal lines is wasted to be inefficient.
Therefore, as one of methods for efficiently performing optical scan with respect to a three-dimensional screen, optical scan in a polar-coordinate (r-θ) direction (hereinafter, referred to as r-θ scan) is considered instead of the X-Y scan. The r-θ scan is realized by combining a rotary action of an optical scanner around a predetermined rotation axis (θ direction) and a one-dimensional scan of the scanner along the rotation axis (r direction).
Here, when drive power is supplied to the optical scanner, formation of wiring is limited due to the rotary action of the optical scanner around the rotation axis. For example, in a case where the wiring is formed from a portion performing a rotary action to other fixed portion, the wiring is tangled due to the rotary action, whereby the rotary action of the optical scanner may be disturbed and the wiring may be damaged.
Therefore, to supply drive power to the optical scanner in a non-contact manner is considered. JP-A-9-91584, as an example, discloses a technique of non-contact power transmission. In the example, in order to take surrounding images by a video camera, drive power is supplied (transmitted) to a rotating body, on which the video camera is mounted in a non-contact manner, by using electromagnetic induction of a magnetic field generating coil.
However, this related art uses the magnetic field generating coil having no magnetic core for the non-contact drive power transmission to the rotating body. Therefore, insufficient power may be supplied to a device and the like which are driving objects. On the other hand, in order to secure sufficient power, a long coil is required, for example, thus requiring a large power supply means disadvantageously.